Lessons Learned and
Challenges for Implementing
Infrared Thermography and
Systems Analysis in Large PV
Solar Plant Arrays
By R. Gillem Lucas
11 July 2013
Who Should Care, If Some Panels or
Parts of PV Solar Plant are 10○C Hotter?
Or the Plant is <90% Efficient?
Relative Comparison of PV
Technology Efficiencies
Let’s Define a Few Terms
1. “Hot” Panel
Let’s Define a Few Terms
1. “Hot” Panel
2. Climograph
3 CLIMOGRAMS
Example Prevailing Winds’ Chart
Example Mean Vector
Wind/Constancy Chart
Mean Scalar Wind Speeds & % of Time with Calms’ Chart
Example of Unexpected Measured
Differential Temperature IR Measurement
∆T> 10○C Across a 20MW PV Solar Plant
Let’s Define a Few Terms
1. “Hot” Panel
2. Climograph
3. “Heat Island” Effect
Example of Measured “Heat Island"
Effect on Very Large PV Solar Plant
Let’s Define a Few Terms
1.
2.
3.
4.
“Hot” Panel
Climograph
“Heat Island” Effect
Varying Efficiency of Solar Panel with
Temperature
Let’s Define a Few Terms
1.
2.
3.
4.
“Hot” Panel
Climograph
“Heat Island” Effect
Varying Efficiency of Solar Panel with
Temperature
5. All Infrared Cameras are Not Equal
Lessons Learned and
Challenges for Implementing
Infrared Thermography and
Systems Analysis in Large PV
Solar Plant Arrays
Lessons Learned Using Aerial IR on
Large (>20MW) PV Solar Plant Arrays
• Manual Walking Inspections to Find Problems with
Panel and String Performance in PV Plants > 20 MW are
Ineffective, Inefficient, and Inaccurate
• We can Detect Non-Uniform Temperature Distributions
Across Both Operating and Non-Operating Individual PV
Panels
• We can Detect Non-Uniform Temperatures among
Multi-Ranked Panels
• Finding Open Strings and “Hot” Panels is Difficult Using
IR Cameras at Ground Level
Lessons Learned Using Aerial IR on
Large (>20MW) PV Solar Plant Arrays
• Detected “Hot” Panels and Defective Panels Can Switch
On and Off
• Not Possible to Conduct Valid Trending Studies without
Accurate Identification of Open Strings, “Hot” Panels,
and other Anomalies during Each Assessment
• Proximity of Ground and Type of Ground Affect Panel
Temperatures
• Advection Co-exists with “Hot Island” Effect
• Predicted Anomalies Associated with Climographs Can
Affect Plant Performance
Lessons Learned Using Aerial IR on
Large (>20MW) PV Solar Plant Arrays
• Each “Hot” Panel can be Associated with a Reduction in
String Output
• The Lack of a Detailed Understanding of “Hot” Panel
Failure Modes and Trending, could Distort Annual and
Cumulative “De-rating Factors”
• IR Examination of the Inverters and the PCS Buildings,
Improvement in the Accuracy of the Inverter
Temperature and Performance Measurements, and a
Thermal Performance Review of the Design and
Operation of the Fully Integrated PCS’s could yield
Reliability and Efficiency Improvements
Lessons Learned Using Aerial IR on
Large (>20MW) PV Solar Plant Arrays
• Greater understanding of production, transportation,
installation, testing, operations, and maintenance can
be achieved through trending studies within individual
plants and through cross‐correlation assessments and
analyses of multiple plants
• The Design of Solar PV Plants can be Dramatically
Improved, Considering Findings from Assessments at
Solar Plants, e.g.
– Making a PV Plant fit a Specific Plot Instead of Optimizing
the Layout of the Plant for Environmental Issues
– Designing the Plant to Minimize “Heat Island Effects”
– Designing the Plant by Considering the Ground Thermal
Conductivity and Local Climographs and Topography
Uncertainties & Complicating
Inaccuracies
• Inability to Actually Cross Correlate Failed Panels
and Electrical Readings
• Temperatures May Vary Significantly If the
Assessment and Survey Takes Too Long
• Significant Variability in Wind Speed and
Direction would Complicate any 3‐D CFD
• Future Development Efforts
• Owners and Operators Prevent Interactive
Problem Solving
Example Efficiency Computations
Computed Loss in Efficiency based upon Assumptions
Net Present
Value (NPV)
of These
Losses Not
Corrected
$
33,975
$
16,987
$ 407,696
$
$
Sub-Total
Sub-Total
Loss in
Loss in Plant
Annual
Output
# or %
Revenue due Efficiency
excess
to this item for this Item
Detected
$
9,581
0.2500% = loss due to # "hot" panels detected
500
$
4,791
0.1250% = loss due to # open strings detected
25
$ 114,975
3.0000% = loss due to decrease in weighted average inverter efficiency from
advertised/specified inverter efficiency
3%
679,493 $ 191,625
5.0000% = loss due to excess (actual-manufacturer specification) weighted
average median panel operating temperature
20 ºC
$
0.0000% = loss due to manufacturer's design weighted average median panel
operating temperature in degrees C above 25 degrees C for plant/field
0 ºC
$ 1,138,150 $
Total Annual
Revenue
Without any
Losses
$ 3,832,500
320,972
8.3750% = Total losses based upon Assumptions
100.0000% = Plant/Field Annual Output under Ideal Manufacturer Conditions
Questions?